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authorJoshua Clayton <stillcompiling@gmail.com>2016-02-05 23:41:11 +0300
committerAlexandre Belloni <alexandre.belloni@free-electrons.com>2016-03-14 19:08:15 +0300
commitb3967067c273359c7462f4be9a887c3d1a515f49 (patch)
tree1f2ca90d34dae4961b97d68ccdb93a979ee5e2b8 /include/linux/rtc.h
parent9d1fa4c3737ac82520931d940dcd2426719f8dd2 (diff)
downloadlinux-b3967067c273359c7462f4be9a887c3d1a515f49.tar.xz
rtc: Add functions to set and read rtc offset
A number of rtc devices, such as the NXP pcf2123 include a facility to adjust the clock in order to compensate for temperature or a crystal, capacitor, etc, that results in the rtc clock not running at exactly 32.768 kHz. Data sheets I have seen refer to this as a clock offset, and measure it in parts per million, however they often reference ppm to 2 digits of precision, which makes integer ppm less than ideal. We use parts per billion, which more than covers the precision needed and works nicely within 32 bits Signed-off-by: Joshua Clayton <stillcompiling@gmail.com> Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Diffstat (limited to 'include/linux/rtc.h')
-rw-r--r--include/linux/rtc.h4
1 files changed, 4 insertions, 0 deletions
diff --git a/include/linux/rtc.h b/include/linux/rtc.h
index 3359f0422c6b..b693adac853b 100644
--- a/include/linux/rtc.h
+++ b/include/linux/rtc.h
@@ -89,6 +89,8 @@ struct rtc_class_ops {
int (*set_mmss)(struct device *, unsigned long secs);
int (*read_callback)(struct device *, int data);
int (*alarm_irq_enable)(struct device *, unsigned int enabled);
+ int (*read_offset)(struct device *, long *offset);
+ int (*set_offset)(struct device *, long offset);
};
#define RTC_DEVICE_NAME_SIZE 20
@@ -208,6 +210,8 @@ void rtc_timer_init(struct rtc_timer *timer, void (*f)(void *p), void *data);
int rtc_timer_start(struct rtc_device *rtc, struct rtc_timer *timer,
ktime_t expires, ktime_t period);
void rtc_timer_cancel(struct rtc_device *rtc, struct rtc_timer *timer);
+int rtc_read_offset(struct rtc_device *rtc, long *offset);
+int rtc_set_offset(struct rtc_device *rtc, long offset);
void rtc_timer_do_work(struct work_struct *work);
static inline bool is_leap_year(unsigned int year)